My truck has been losing a little coolant for a few months now. I notice that the reserve coolant tank will start to dry up or lose coolant. it does not seem to do it with any regularity, 2 weeks will be the same level, then all of a sudden its half empty. the trucks temp according to my ultraguage is 95% of the time between 176-181 degrees. if im flying up a hill or something it will get to 185 or something. i have never had overheating issues.

Here are the facts. There is most def a leak, its either the thermostat housing, or the lower intake gasket. the coolant is mostly being leaked into the V valley of the top of the engine, directly behind the thermostat, i see a pool of green coolant resting there. sometimes if i go up a steep incline or whatever, it will drip down the back of the engine and hit the ground under the tranny. Most of the time, there is a small leak on the front, passenger side of the engine, meaning that there looks to be crusted green slime that trails down, looks like green pond scum. it will drip only up to like a palms worth of coolant and it drips down from the passenger side lower control arm.

another random thing i noticed is when the truck is parked so that the passenger side front is a lower incline than the rest of the truck, it leaks more. but if the truck is on an upward incline it doesnt do it as much.

I checked the thermostat housing, and from what i can see, because the view is awful, it looks likethe 2 medium hoses on top that go into the housing have some light, green crusting around the end of the hose wheere it goes in the plastic. i put my hands around the housing as best i could but could not feel a definite wet spot or anything but there is def evidence of crusting(light) on the housing where i can see it.

Do you guys think i hsould just break down and do the housing and the thermostat? its not an awful leak but im **** and its highly irritating. Is the stock thermostat 195? would anything happen if i used a 190 or 185? would i need supporting mods? any advice would help.

 

i would change the housing out...there shouldnt be any deposits around the hoses to begin with...i think you should be fine running a cooler t-stat

 

is there any site that would be recommended for the t housing and tstat? i dont wanna autozone it, i want a reputable source that is cheaper than the dealer.

also, it looks like the crust is mostly toward the bottom of the housing unit, like underneath the big upper radiator hose. is that still a part of the housing or an entirely different part?

 

rock auto


not sure on that one

 

If you have the SOHC engine, it's probably leaking from the housing to head gasket. Common. You cannot get the damn gasket by itself, and the housing is a Ford-only special order part a few days away costing a couple hundred dollars. Comes with new gasket, thermostat + gasket, and ECT sensor.

What I have done is remove the assembly, clean everything up, grind the brass fittings in the plastic housing flush again (they pull out over time), and bolt it all back together.

 

It is almost certainly the "o"ring on your thermostat housing. Sadly, you can't really get to it without taking off the intake manifold. It is not as hard as it seems. Do a search and find the correct instructions. It is just time consuming. You will need to replace the intake gaskets set as well, but that will fix your leak. My truck did the same thing and I put it off for awhile, but it won't go away.

Do yourself a favor and fix it right. You may have to get a new thermostat housing, but probably not. Might as well replace the thermostat while you are at it. Watch out for the two sensors. Be very careful, but it is probably better to replace them too. They generally won't re-seal once you have taken them out of the housing. Been there, done that.

Good luck and have fun!

 

Go ahead and get a "stock" or "factory" temp thermostat, a cooler running one is not good for any modern computer controlled, fuel injected motor. You mileage will go down and so will your power....the hotter you can burn the fuel the more complete a combustion you get....getting a lower temp stat hinders the thermodynamic efficiency hurting mileage/power. These days modern motors operate within much tighter temperature parameters and a lower running temp is not what the motor needs, as then the motor can never fully reach optimum operating temp and burn the fuel will less thoroughness.

 

You can get the upper thermostat housing out without removing the intake manifold. I just replaced mine a few weeks ago. Its a tight fit but it will come out. You can get an O-ring at any parts store for a couple bucks. Just make sure to line up the thermostat with the housing for re-assembly, its molded so it will only fit a certain way....you'll see when you take it off.

And I vote for a stock (190-195 degree) thermostat. And since its only a few more dollars ($12 I think) and since you already have the housing off, replace it also.

If its leaking from the lower housing then yea...you gotta get the new ford part and thats not cheap.

 

You mean the lower thermostat housing? if you do, its a 10 dollar part from autozone.....

 

Dunno about you in California, but here on the east coast, the entire housing assembly is a Ford part, or Dorman. Either is a special order part, and is at minimum 3-4 days away for around $200-250.

IIRC, last time I checked, the Dorman aftermarket one was a manufacturer special order item, so it was 2 weeks away. This was through Autoparts Warehouse.


This is a 4.0L SOHC item, and you do NOT need to remove the intake manifold to get at this thing. Pull the alternator and it is right there, bolted with 3 long bolts to the passenger side cylinder head.

 

yeah i think i can get it without taking the alternator off, maybe just the cables to it for more room, im not worried about doing the actual job, was just making sure i had all the exits covered so i dont have to do double work or get the wrong part.

 

Yeah you probably can wiggle it around the alternator. Last time I did one I pulled the alt just because it was only 3 bolts and made it easier to see what I was doing.

 

I didn't take anything off. Just the air intake tube, throttle body, and slid the upper housing out after taking out the 3 bolts. It's really not hard.

 

Cool. I think im gonna tackle this in the next couple weeks. I got a parts list from Ford. I think ill stay w the stock 190 degree just for simplicity

 

Any updates on this guys? I just developed a leak on the passenger side near the front of the head and it runs down the front passenger side corner of the block. I feared it was the head gasket till I called the local parts store (lordco) and they tell me that they do not stock the head gasket set and have never sold one - this tells me that head gasket failure is not too common.

Anyone have pics of the job? I am wondering why the lower (or upper housing) needs to be replaced - does it crack? Why can it not be sealed with RTV?

4.0 SOHC

 

First, are you sure its coming from your T-stat and not the hose connecting to your Tstat? Second, it wouldnt be your headgasket if the coolant is leaking on the ground... Thats only if its going in your oil or exhaust gasses are entering your coolant system.


Find the leak for sure. If its your hose, it could run down the side of the t-stat housing and drip from there, making you think the leak is on the engine, when its just a split/tear/pinhole in your hose.

 

Just found the exact same problem on my truck. I picked up a new o-ring from autozone and I'm going to tackle it tonight after work. I'm hoping it's not a cracked housing. I'll find out more when I get the intake stuff out of the way.

 

i just fixed my lower thermostat housing and intake gaskets. took maybe 2-3 hours to do. I found the lower thermostat housing for 50 bucks. came with all gaskets and bolts included the top cover and everything.

 

i had the same problem 6 months ago. turned out to be the thermostat housing. dealer part. got it replaced at a shop for about $140.

 

Where did you find it? E-bay special or ?

 

I found a housing, T-stat, o-ring, the whole kit essentially for $26 from Rock Auto, the sensors for about $24 total, and all the hoses from Rock Auto. I was getting a pool of coolant on the V of my engine behind the housing, there was a crack in the lower housing. Had to take the intake off to get to it, ended up tearing off a bolt, and filling it in and re-threading it for the bolt. Put it all back together without the o-ring and T-stat to flush it with distilled water, and it all poured down to the ground, we didn't realize the o-ring would do so much lol we'll finish that next weekend.

 

Thanks for the posts on V6~4.0L~SOHC engines & TStat housings; good reference info.
Replaced the old leaking FRPlastic TStat Housing with a new Aluminum TStat Housing
in 2019Aug on a 2001 Ford ExSportTrac; no leaks as of 2020Mar after ~5K more miles.
My full write up with pics on that repair:
http://2001fordexplorersporttrac.fandom.com/Coolant_ThermoStat_Housing